Infrared kinetic spectroscopy

U. Simon, C.E. Miller, R.F. Curl, F.K. Tittle A widely tunable difference frequency source for infrared kinetic spectroscopy. Proc. Int l Conf. Laser 92 (STS Press, McLean, VY 1993)... 

The objective of the present work was to determine the influence of the light intensity on the polymerization kinetics and on the temperature profile of acrylate and vinyl ether monomers exposed to UV radiation as thin films, as well as the effect of the sample initial temperature on the polymerization rate and final degree of cure. For this purpose, a new method has been developed, based on real-time infrared (RTIR) spectroscopy 14, which permits to monitor in-situ the temperature of thin films undergoing high-speed photopolymerization, without introducing any additive in the UV-curable formulation 15. This technique proved particularly well suited to addressing the issue of thermal runaway which was recently considered to occur in laser-induced polymerization of divinyl ethers 13>16. 

The mechanism of dissolution of the Cu UPD layer on Au(lll) has been studied by Ataka etal. [409]. The monolayer comprised Cu in 2/3 and sulfate in 1/3 proportions. It has been found by applying time-resolved surface-enhanced infrared absorption spectroscopy and chronoam-perometry that dissolution proceeds in two steps. In the first step, 1/3 Cu monolayer and all sulfate anions are removed via the Langmuir-type kinetics. In the second step, the rest of Cu is desorbed via nucleation and growth kinetics. 

In principle, absorption spectroscopy techniques can be used to characterize radicals. The key issues are the sensitivity of the method, the concentrations of radicals that are produced, and the molar absorptivities of the radicals. High-energy electron beams in pulse radiolysis and ultraviolet-visible (UV-vis) light from lasers can produce relatively high radical concentrations in the 1-10 x 10 M range, and UV-vis spectroscopy is possible with sensitive photomultipliers. A compilation of absorption spectra for radicals contains many examples. Infrared (IR) spectroscopy can be used for select cases, such as carbonyl-containing radicals, but it is less useful than UV-vis spectroscopy. Time-resolved absorption spectroscopy is used for direct kinetic smdies. Dynamic ESR spectroscopy also can be employed for kinetic studies, and this was the most important kinetic method available for reactions... 

IRDLKS = infrared diode laser kinetic spectroscopy, investigation of the rotational structure of the l 2 band MW = microwave spectroscopy ED = electron diffraction ES = electronic spectroscopy, investigation of the rovibronic structure of electronic transitions bond angles calculated from isotopic shifts of the 03 bands of triatomic CAs are not presented here due to their large experimental error these values are reported in Section VI. 

For the assay of enzymes with products and reagents that have no absorption, fluorescence or luminescence in the ultraviolet or visible region, developments in analytical infrared spectroscopy can be used. In particular, mid-Fourier transform infrared (mFTIR) spectroscopy has been successfully applied to the determination of enzyme activities and kinetics, e.g. of /i-fructosidasc, phosphoglucose isomerase and polyphenol oxidase [90]. The method could very well be a tool that may also be applied to a variety of other enzyme classes. The potential of high-throughput applications, however, has yet to be demonstrated. 

IRDLKS infrared diode laser kinetic spectroscopy... 

While 32 itself is hydrolytically inactive, the singly deprotonated form (33) mediates the hydrolytic cleavage of picolinamide (but not acetamide) in ethanol to finally give 35 (Scheme 5). Kinetic data and infrared (IR) spectroscopy suggest a substrate binding pre-equihbrium with a binding constant of picolinamide in 34 of... 

From the analysis of the data in the LIPID AT database (41), more than 150 different methods and method modifications have been used to collect data related to the lipid phase transitions. Almost 90% of the data is accounted for by less than 10 methods. Differential scaiming calorimetry strongly dominates the field with two thirds of all phase transition records. From the other experimental techniques, various fluorescent methods account for 10% of the information records. X-ray diffraction, nuclear magnetic resonance (NMR), Raman spectroscopy, electron spin resonance (ESR), infrared (IR) spectroscopy, and polarizing microscopy each contribute to about or less than 2-3% of the phase transition data records in the database. Especially useful in gaining insight into the mechanism and kinetics of lipid phase transitions has been time-resolved synchrotron X-ray diffraction (62,78-81). 

The kinetics of the reaction of NO with methyl radicals in the presence of acetone as the bath-gas was studied by Jodkowski et al,212 using time-resolved infrared absorption spectroscopy. The kinetics of CH3 + NO was studied under pseudo-first-order conditions, i.e. with [NO] [CH3], while the contribution from the self-reaction of methyl radicals... 

To investigate the kinetics that control the rate of network connection of a highly cross-linked photopolymer system, Lovell et al. (2001) utilized rapid scan near-infrared (NIR) spectroscopy to study the polymerization of a dimethylacrylate dental resin. The research exploited the Thermo Electron rapid-scan capabilities to analyze the system with a time resolution of ss 30 ms. This was sufficiently faster than traditional techniques, which required data collection at the 2-second time scale and would thus miss the reaction of interest that reacts to... 

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